Clutch cover and clutch comprising such a cover

ABSTRACT

A clutch cover having balancing holes (31) for fixing a balancing device. At least one recess (32) is formed in the cover adjacent to one of the balancing holes (31) wherein the recess reduces the local thickness of the cover plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to cover plates for clutch mechanisms,especially for motor vehicles, and to clutch mechanisms including such acover plate, as is described for example in the document FR-A-2 585 424.

2. Description of the Prior Art

As is known, a clutch mechanism includes a unitary assembly of annularcomponents, namely a cover plate, a pressure plate which is usually acasting, and axially acting resilient means which usually consist of adiaphragm.

The cover plate is adapted to be attached on a reaction plate which, inits application to motor vehicles, is arranged to be fixed on thecrankshaft of the engine of the vehicle. The pressure plate offers afriction face for a clutch friction wheel which, in a motor vehicle, ismounted on the input shaft of the gearbox for rotation with it.

The clutch is accordingly a rotating component, and for this reason itis necessary to balance it dynamically. This dynamic balancing isusually obtained by means of holes formed in the pressure plate. Such asolution is not entirely satisfactory because it leads to the occurrenceof hot spots in the region of the said holes.

For this reason it is preferable to carry out the said balancing withthe aid of balancing members, such as balancing rivets which are fittedin holes formed in advance in the cover plate. Thus, with the aid of amachine it is possible to determine the location at which the saidbalancing member or members are to be fitted.

In order to obtain fine balancing, piercing of the balancing member ormembers can be considered. A result of this can be that, during thepiercing operation, the balancing member is caused to rotate, and thisis detrimental to its fastening on the cover plate.

An object of the present invention is to mitigate this drawback in asimple and inexpensive way, and accordingly to provide novel means whichwill enable rotation of the balancing member to be prevented.

SUMMARY OF THE INVENTION

According to the invention, a cover plate for a clutch mechanism of thetype defined above is characterised in that at least one rebate isformed in the cover plate in the vicinity of a fastening hole for thebalancing member, and in that the rebate consists of a recess whichreduces the local thickness of the cover plate.

Thanks to the invention, during fastening of the balancing member, someof the material of the said member is able to penetrate into the saidrebate in such a way that the balancing member is prevented fromrotating by mating cooperation. It is therefore possible to pierce thebalancing member subsequently without any risk of the latter becomingdislodged.

Accordingly, the recess does not extend from one side of the cover plateto the other, so that while the balancing member is being upset, theresulting flow of material is more closely controlled. In addition, thecover plate retains its rigidity.

To this end, the balancing member is preferably fitted on the coverplate by carrying out an upsetting operation. The said member preferablyconsists of a balancing rivet with a head of tubular form, which isadapted to be pierced in order to obtain fine balancing.

Preferably, the recesses are of oblong form and are open at one of theirends radially into the hole in the balancing member.

In order to enhance the blockage against rotation, a plurality ofrebates or recesses are preferably formed in the vicinity of the hole inwhich the balancing member is fastened. These recesses or rebates may bein a form like that of petals projecting from a heart, which isconstituted by the fastening hole.

In accordance with the invention, a clutch mechanism of the type definedabove is characterised in that it includes a cover plate according tothe invention.

The following description illustrates the invention with reference tothe attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in axial cross section of a clutch mechanism inaccordance with the invention;

FIG. 2 is a view on a larger scale of a detail of FIG. 1, correspondingto the box 11 in FIG. 1;

FIG. 3 is a view in elevation of a cover plate in accordance with theinvention;

FIG. 4 is a view on an enlarged scale showing a detail of FIG. 3corresponding to the box IV in FIG. 3;

FIG. 5 is a view on an enlarged scale of a detail of FIG. 3,corresponding to the box V in FIG. 3;

FIG. 6 is a partial view, in cross section taken on the line VI--VI inFIG. 5;

FIG. 7 is a view similar to FIG. 6, with a balancing member fitted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show a diaphragm clutch mechanism for motor vehicles. InFIG. 1, the reaction plate and the clutch friction wheel which areincluded in a clutch are shown diagrammatically at 100 and 101respectively. In the known manner, a clutch for a motor vehiclecomprises a reaction plate 100, a clutch friction wheel 101, and aclutch mechanism which includes a unitary assembly consisting of annularcomponents, namely: a cover plate 1 which is typically a componentpress-formed from sheet metal, a pressure plate 5, which is usually acasting, and axially acting resilient means 6.

In this example, the resilient means 6 consist of a diaphragm, while thecover plate 1, which is in the form of a hollow dish, includes a baseportion which is orientated generally transversely and which has acentral through aperture. The said base portion is extended at its outerperiphery by a skirt portion, which in this example surrounds thediaphragm 6 and the pressure plate 5. The said skirt portion is itselfextended by a generally transversely orientated flange that extendsradially away from the axis of the assembly.

This flange accordingly defines the outer periphery of the cover plate1, and includes a first set of coplanar portions through which it isarranged to be fixed on the reaction plate 100. The said flange also hasa second set of coplanar portions 3, which are displaced axially backwith respect to the portions 2, and by means of which it is attached tothe pressure plate 5, in a manner known per se, by means of resilienttongues 4, which in this example are orientated tangentially, thepressure plate being thus coupled to the cover plate but with freedom tomove axially.

In this example, the portions 2 include holes 21, 121 (FIG. 3), throughwhich there pass, respectively, the fastening member by which the coverplate 1 is secured to the reaction plate 100, and centring pins carriedby the reaction plate 100. The portions 3 are also formed with throughholes for mounting return tongues 4 which are fixed, by means offastening members, at one of their ends to radial lugs of the plate 5,and at their other ends to the portions 3 through the said holes.

The diaphragm 6 has a peripheral portion in the form of a Bellevillering 7, and a central portion which is divided into radial fingers 8 bymeans of slots 9. In this example widened passages 10 are formed betweenthe fingers 8 at the radial level of the root zone where the fingers 8join the ring 7. The diaphragm has a frusto-conical form in the freestate. The outer periphery of the Belleville ring 7 acts on a dividedannular projecting element (not given a reference numeral in FIG. 1) ofthe pressure plate 5, while the inner periphery of the said ring 7 bearson a primary abutment 11, which in this example is defined by apress-formed projecting element which is formed in the base portion ofthe press-formed sheet metal cover plate 1.

The clutch is normally in its engaged condition, and the diaphragm 6bears on the projecting element 11 so as to act on the projectingelement of the pressure plate 5, in order to grip the friction liners ofthe clutch friction wheel 101 between the pressure and reaction plates.In order to disengage the clutch, it is necessary to exert a thrust onthe ends of the fingers 8, in the direction of the arrow A in FIG. 1, bymeans of a clutch release bearing (not shown), so as to cause thediaphragm to deflect and to cause it to cease acting on the pressureplate 5.

The tongues 4 thus urge the plate 5 towards the base portion of thecover plate 1. For this purpose, the diphragm 6 is mounted for pivotingmovement on the cover plate 1, by assembly means which apply thediaphragm pivotally to the cover plate. In this example, these meansinclude the primary abutment 11 mentioned above, together with fasteninglugs 12 and a frusto-conical crown 13. The lugs 12 project integrallyfrom the base portion of the cover plate, being formed by stamping andbending, and in the present case they are arranged alternately withabutment lugs 22 which are orientated generally transversely.

Some of the abutment lugs, namely the lugs 122, are formed with notches123 so as to define a locating element. As can be seen in the lower partof FIG. 1, the fingers 8 engage on the lugs 22 when the clutch mechanismis not fixed on the reaction plate 100. After the mechanism has been sofixed, the diaphragm 6 is generally flat when the clutch friction wheel101 is new.

In a manner known per se, the fastening lugs 12 include an axial portion14 which passes through the passages 10 in the diaphragm, together witha radial terminal wing portion 15 which is bent radially away from theaxis of the assembly along a line of weakening 16 (FIG. 2), so as todefine a locating bend, and this enables the crown 3 to be mountedbetween the diaphragm 6 and the wing portion 15. The periphery of thecrown 13 offers a secondary abutment 17 to the diaphragm 6, in alignmentwith the primary abutment 11.

The abutment 17 is formed on a rounded outer edge 21 of the crown 13,which has at its inner periphery edges 22, 23 in contact with theportion 14 and the wing portion 15 respectively. A rounded zone joinsthe projecting element 11 to the axial portion 14 of the lugs 12. Thediaphragm is thus mounted pivotally between the said abutments 17 and11, and during disengagement of the clutch, the diaphragm 6 bears on thesecondary abutment 17, which in this example is elastic.

Having regard to the foregoing, it will be noted that the clutchmechanism constitutes a rotatable unitary assembly which must bedynamically balanced, for safety reasons in particular. To this end, thecover plate 1 is formed with holes 31, referred to as balancing holes,for the fitting and fastening of balancing members 132.

In accordance with the invention, a cover plate of the type describedabove is characterised in that it has at least one rebate 32 formed inthe vicinity of a balancing hole 31, and in that the rebate consists ofa recess which reduces the local thickness of the cover plate. Therebate 32 is oblong in shape, and is open radially at one of its endsinto the aperture or hole 31. The other end of the rebate 32 is ofsemicircular form (FIG. 6). In a modified version, this end may beinclined.

In this example, each hole 31 has four rebates 32. These rebates arespaced apart circumferentially at regular intervals of 90 degrees withrespect to each other. The rebates thus extend generally radially, withtwo pairs of diametrically opposed rebates. In this example, the holes31 are formed in the outer peripheral flange of the cover plate. Theholes 31 are formed in coplanar portions 30 of the flange, which areoffset axially with respect to the above mentioned portions 2 and 3.These portions 30 are in this example spaced apart by 120 degrees withrespect to each other, with each portion 30 having two holes 31, withtheir rebates 32, for the fitting of balancing members 132. In thisexample these members 132 consist of rivets.

As will have been understood, during the fastening, by upsetting, of therivet 132 in one of the holes 31, the material of the said rivet iscaused to flow and thus to fill the rebates 32, which are preferablyshallow, so that a mating cooperation is obtained between the rivet andthe cover plate, thus preventing rotation of the rivet in the coverplate as can be seen in FIG. 7, in which the deformation which the tailof the rivet 132 undergoes during the upsetting operation isexaggerated.

The said rivet has a cylindrical head, which in this example is in theform of a boss. The invention makes it possible to pierce this head, at133, so as to provide fine adjustment for the balancing of the mechanismusing a balancing machine, which selects the hole or holes 31 in whichthe rivet or rivets 132 are to be fitted. These rivets 132 mayaccordingly be pierced after having been fitted, without any risk ofrotation.

The balancing rivets 132 are thus firmly secured, and there is no needto modify the tooling in any significant way for manufacture of thecover plate.

The present invention is of course not limited to the embodimentdescribed, and in particular the fastening holes for the balancingmembers may be formed, for example, in the coplanar portions 3, or, in amodified version, given that this may be detrimental to inertia, theymay be formed in the abutment lugs 22.

It is possible to use, in place of balancing rivets, other balancingmembers which are preferably secured by seaming.

The diaphragm may be mounted pivotally on the cover plate by means ofabutment rings which are carried by the fastening lugs 12, or, in amodified version, by means of spacer bars. The clutch may be of thepull-to-release type, the diaphragm then bearing on the cover plate (atits outer periphery), and on the pressure plate.

In place of a diaphragm, the clutch mechanism may of course include coilsprings and clutch levers, with the said springs acting between thecover plate and the pressure plate.

A clutch cover having balancing holes (31) for fixing a balancingdevice. At least one recess (32) is formed in the cover adjacent to oneof the balancing holes (31) wherein the recess reduces the localthickness of the cover plate.

We claim:
 1. A cover plate for a clutch mechanism made of metal having athickness, said cover plate comprising balancing holes (31) for thefitting of balancing members (132), wherein at least one recess (32) isformed in the cover plate vicinity of a level with one of said balancingholes (31), the recess (32) reduces a local thickness of the metal andthe recess (32) has an oblong form and which is open radially at one endadjacent the balancing hole.
 2. A cover plate according to claim 1,wherein the other end of the recess (32) is of semicircular form.
 3. Acover plate according to claim 1, wherein the recess is shallow.
 4. Acover plate according to claim 1, wherein said cover plate includes, atthe level of each balancing hole (31), four recesses (32) which areorientated generally radially and which are spaced apart from each otherby 90 degrees.
 5. A cover plate according to claim 1, having a generallytransversely orientated peripheral flange, with first coplanar portions(2) for fastening the cover plate to a reaction plate (100) of theclutch, wherein the balancing holes (31) with their associated rebates(32) are formed in said flange, in coplanar portions (30) thereof whichare offset axially with respect to the first coplanar portions (2).
 6. Aclutch mechanism comprising a cover plate according to claim 1 (1), apressure plate (5) coupled in rotation to the cover plate (1) butmovable axially with respect thereto, and a diaphragm (6) which ismounted pivotally on the cover plate (1) so as to act on the pressureplate (5).
 7. A clutch mechanism according to claim 6 wherein saidclutch mechanism includes at least one balancing rivet (132) with apierced head, and in that said rivet (132) is mounted in the balancinghole (31), being prevented from rotating by the recess (32) associatedwith the balancing hole (31).